Description:

While phytoplankton generally have crucial roles in marine ecosystems, a small subset can release toxins and produce harmful algal blooms (HABs). HABs can be a threat to human health as symptoms from exposure range from neurological impairment to gastrointestinal (GI), dermal, and/or respiratory illness. The objective of this study was to evaluate the association between phytoplankton in marine water and symptoms of illness.
During the summer of 2009, beachgoers were recruited into a prospective study at Boquerón Beach, Puerto Rico. On the day of the beach visit, study participants were interviewed for baseline health conditions and activities engaged in at the beach. Also, water samples were quantitatively assessed for phytoplankton (total and group cell counts), and two algal toxins (lyngbyatoxin and debromoaplysiatoxin). A follow-up telephone interview was conducted 10-12 days later to determine if exposure had resulted in the development of any symptom of illness. Logistic regression models were used to describe the association between exposure to different categories of phytoplankton and incidence of illness among participants who reported immersing their body in the water. Cell counts were categorized as high (≥75th percentile), medium (25th-75th percentile), and low (≤25the percentile). The lowest category served as the referent in the regression models. All results were adjusted for potential confounders.
Of 15,726 study participants, 12,111 (77%) reported immersing their body in the water and were included in the analysis. Daily total phytoplankton cell counts ranged from 346 to 2,012 cells/mL (median: 712 cells/mL). The 3 most frequently identified algal groups were bacillariophyta (median: 386 cells/mL), cyanobacteria (132 cells/mL), and pyrrhophyta (37 cells/mL). Concentrations of lyngbyatoxin and debromoaplysiatoxin were below the limit of detection. Respiratory illness was the most commonly reported symptom of illness (7%), followed by GI illness (5%), rash (5%), eye irritation (3%), and earache (2%). The high category of total phytoplankton cell count was associated with eye irritation (Odds Ratio=1.32; 95% confidence interval: 1.03-1.69) and rash (OR=1.28; 95% CI: 1.03-1.59). The medium category of bacillariophyta was associated with respiratory illness (OR=1.27; 95% CI 1.06-1.52), however, the odds ratio did not increase with the highest category (OR=1.09; 95% CI: 0.88-1.35). The associations for respiratory illness, eye irritation, rash, and earache all appeared to rise with increasing category of cyanobacteria. The most apparent association was for respiratory illness, with the highest cyanobacteria category having OR= 1.37 (95% CI: 1.12-1.67) and the medium category having OR=1.29 (95% CI: 1.07-1.55). Symptoms of illness were not associated with exposure to pyrrhophyta.
Our findings suggest that there may be an association between marine phytoplankton and illness. In addition, these risks may vary by algal group. However, because cell counts were so low, we cannot determine whether the association was a result of the algal exposure or if the phytoplankton were markers for other causative factors we did not measure. This abstract does not necessarily represent EPA policy.

Purpose/Objective:

Marine phytoplankton concentrations were measured during a larger study of beachgoer health and recreational water quality. Surprisingly, we found health effects were associated with relatively low concentrations of total and group-specific phytoplankton. This is the first study of health effects associated with low phytoplankton concentrations. Further work is needed to confirm this association.